Trim-correcting facility for ground effect machines

ABSTRACT

An air cushion suspension system for a ground effect machine comprising in combination a movable disc bearing cushioncontaining means and balanced by the cushion pressure acting on one side of the disc and by an opposing pressure acting on the opposite side of the disc, the opposing pressure existing in a deformable suspension chamber in which a tubular air chamber is disposed, the tubular air chamber being adapted to be inflated to a pressure above the opposing pressure and to bear against the disc to provide extra stiffness in the suspension. The flexible wall of the tubular air chamber is, in the balanced state and with the machine operating normally, clear either of the disc of the suspension chamber wall opposite the disc, so that the extra stiffness is introduced into the suspension only with effect from a particular amount of deformation of the disc suspension chamber, the tubular air chamber forming a kind of resilient abutment.

Bertin et al.

[11.] 3,797,399 Mar. 19, 1974 TRIM-CORRECTING FACILITY FOR GROUND EFFECT MACHINES [75] Inventors: Jean Henri Bertin,

Neuilly-sur-Seine; Francis Marie Jean Croix-Marie, Viry Chatillon, both of France [73] Assignee: Societe De LAerotrain", Paris,

France [22] Filed: Mar. 9, 1972 [21] Appl. No.: 233,177

[30] Foreign Application Priority Data Mar. 11, 1971 France 71.08487 Feb. 8, 1972 France. 7204125 52 us. on '104/23 FS, 180/121 [51] "Int. Cl 1361b 13/08 [58] Field of Search 104/23 FS. 134; 180/116, 1 ISO/117,118,120, 121,124

I [56] References Cited UNITED STATES PATENTS 3.185.240 5/1965 Eggington. 180/116 3.118.659 1/1964 Paulsen 267/35 3.581.667 6/1971 Bertin... 180/116 3.685.607 8/1972 180/116 Eglen Hart 1. 104/23 F5 Bertin.. 180/121 Primary ExaminerGerald M. Forlenza Assistant Examiner-D. W. Keen Attorney, Agent, or Firm-A. W. Breiner 5 7 ABSTRACT The flexible wall of the tubular air chamber is, in the balanced state and with the machine operating normally, clear either of the disc of the suspension chamber wall opposite the disc. so that the extra stiffness is introduced into the suspension only with effect from a particular amount of deformation of the disc suspension chamber, the tubular air chamber forming a kind of resilient abutment.

12 Claims, 9 Drawing Figures PATENTEDMAR 19 I974 SHEET 3 UF 4 PATENTEDMAR 19 m4 SHEET l 0F 4 l I: ill

TRIM-CORRECTING FACILITY FOR GROUND EFFECT MACHINES This invention relates to pneumatic suspensions for ground effect machines, inter alia cushion vehicles whose cushions are contained by skirts secured to a disc or the like which is maintained in a balanced state by the cushion pressure, acting on one side of the disc, and by an opposing pressure existing in a suspension chamber and acting on the opposite side of the disc. The suspension chamber is deformable and has one wall formed by a hermetic cloth whose tension may or may not be added to the pressures acting on the skirt bearing disc.

In the case of a guided machine, e.g., a machine guided along a T-shaped track, the invention is of use for thelift cushions and/or the guide cushions.

It is an object of the invention so to devise a suspension of the kind described that the vehicle becomes less sensitive to external forces and less likely to be tilted by a cross-wind or centrifugal force; according to the invention, the chamber at the opposing pressure receives a tubular air chamber adapted to bear on the said opposite side of the disc and inflated to a pressure'which is, with advantage, adjustable and which is equal to or above the opposing pressure.

According'to a feature of the invention, the tubular air chamber is inflated by pressure fluid taken directly from the cushion supply circuit, such fluidbeing sampled in parallel with pressure fluid intake means forthe air suspension chamber with less lossof head than in the lastmentioned means, so that the pressure in the tubular air chamber is above the pressure of the suspension chamber, in which it is disposed. According to a feature of the invention, the tubular air chamber is inflated from a main pressure intake on the delivery side of the cushion supply fan, advantageously upstream of the intake ducts. M p

Alternatively, the tubular air chamber is inflated by means of a static pump whose diffuser which is, with advantage, in shape convergent-divergent has a valve or other similar delivery-controlling facility disposed either downstream of or near the diffuser throat. Additionally or alternatively, the inducing delivery of the static pump (or more usually the pressure output by the means for inflating the tubular air chamber) is controlled in dependence upon appropriately detected variations of conditions likely to affect machine trim. Such variations include crosswind effects, turns of the machine and out-of-balance conditions of the payload. In the case of a machine adapted to move along a track with the interposition of lift cushions producing a vertical lifting force and oppositely disposed guide cushions producing balanced horizontal forces, the inducing delivery of the static pump for inflating a tubular air chamber (or the output pressure of the inflating means) for use in the suspension of'alift cushions and possibly of a guide cushion is controlled, in accordance with a feature of this invention, by a detector detecting the difference between two opposite guide cushions, the last-mentioned inducing delivery being dependent upon the absolute pressure difference thus detected.

According to another feature of the invention, the tubular air chambers can be inflated from pressure intakes disposed at appropriate outside positions on the machine. For instance, there can be considered dynamic pressure intakes facing towards the front of the machine or sidewind intakes opening on to the machine sides, in which latter event the tubular air chamber is supplied via a distributor controlled by a detector sensitive to such a sidewind pressure.

According to another feature of the invention, the flexible wall of the tubular air chamber is, in the balanced state and with the machine operating normally, clear of one of the opposite and relatively movable walls of the suspension chamber, so that extra stiffness is introduced into the suspension only with effect from a threshold compression thereof, the tubular air cham ber forming a kind of resilient abutment secured to just one of the opposite walls.

The following exemplary non-limitative description, taken together with the accompanying drawings will show clearly how the invention can be carried into effeet. In the drawings FIG. 1 is a very diagrammatic view in partial vertical section to show the underlying system provided by this invention;

FIG. 2 is a cross-sectional view of the bottom part of an air/cushion vehicle (ACV)'guided along an inverted-T track;

FIG. 3 is a view similar to FIG. 2 but to an enlarged scale and showing a constructional detail;

FIG.4 is a diagrammatic plan view of an embodiment of this invention;

FIG. 5 is a diagrammatic view in partial vertical section showing improvements provided by this invention;

FIG. 6 is a cross-sectional view of the top part of a vehicle guided below an inverted-T track;

FIG. 7 is asimilar view to FIG. 5 and shows a variant of the air supply system;

FIG 8 is a diagrammatic plan view form of this invention, and FIG. 9 is a diagrammatic partial cross-sectional view of the bottom part of a pressure-fluid-cushion vehicle guided above an inverted-T track.

FIG. 1 shows body l of a machine moving above a surface 2 which can be a prepared track; between surface 2 and the machine is a pressure-fluid-cushion 3 supplied through one or more orifices 4 and contained by peripheral skirts 5 secured to a disc or plate or the like 6 hingeable around a hinge 7. Disposed between base 8 of body I and the edge of integer 6 is a hermetic cloth 9 forming a flexible wall for an enclosure or chamber 10 communicating by orifices 4, 11 with a pressure fluid source.

Plate or disc 6 is acted on by pressure P1 of cushion 3 and by a pressure P2 operative in chamber 10; integer 6 also experiences the stressing of cloth 9, such stressing depending upon distance y between integer 6 and body base 8 and upon pressure P2.. Integer 6 stabilises in an equilibrium position for a particular value of spacmg y- The constructional details and operation of a suspension thus devised are disclosed in French Pat. No. l,603,l 14 of June 28, 1968 to which reference can be made if required.

Basically, the improvement which this invention provides in such a suspension is the provision in the chamber 10 of one or more tubular air chambers 12 which bear on body base 8 and on plate 6 and which are inflated to an adjustable pressure P3, P2. The extra tubular air'chambers 12 act in three ways:

1. They can provide an extra stiffness which is additive to the stiffness of the suspension.

of a preferred 2. The extra stiffness can be controlled by actio n on e pts tqllt V U a 3. The suspension can have its initial characteristics restored if P3 is made equal to P2.

As shown in FIG. 1, the flexible wall of each tubular air chamber 12 can be secured to the integers 6 and 8 just along a single generatrix a, b respectively. Preferably, securing is by means of internal plates 13, 13 as shown in FIGS. 2 and 3, with the advantage that the extra stiffness provided by the tubular air chamber 12 is greater than in the case just described in which there is contact along generatrices. So that the use of the integer 12 does not introduce any disturbing force into the suspension, at the value of the spacing y corresponding to equilibrium the two opposite segments 12a and 12b of the flexible wall of the tubular air chamber should be arcs of the same circle i.e., the tubular air chamber 12 should in geometric shape resemble a circular cylinder intersected by the plates 13, 13.

The pressure P3 can be dependent upon sidewind pressure through the agency of pressure intakes on the sides of body 1. Alternatively, the pressure P3 can be dependent on the centrifugal force acting on the vehicle when the same negotiates bends.

The improvement of the invention is of equal use for horizontal lift cushions and for horizontal guide cushions, as can be seen clearly in FIG. 2 for an inverted T.

Preferably, the integers 12 are pressurised to the pressure P3 by way of static pumps 16 which are shown in FIG. 4 and which intake in the chamber 10; consequently, at rest i.e., in the absence of primary stream from the inducing nozzle 14 of the static pump 16 the pressure in the integer 12 is the same as the pressure in the chamber 10 i.e., P3 P2.

In the example shown the inducing flow is provided by a gas-turbine engine M by way of a manually or automatically controlled valve whence supply ducts C, C extends over the full length of the vehicle so as to supply all cushioris, the nozzle 14 of the pumps 16 being connected to the ducts C.

In the example shown, which is of use with rectangular cushions having four containing means of the kind hereinbefore described, any two consecutive integers as 12, 12' are supplied by a single static pump 16 through a flexible communicating hose 15.

In the embodiments hereinbefore described the flexible material of the integers l2 is'secured to the integers 6 and 8 by way of an integer 13; in a variant, however, such wall is secured just to one of the integers 6 or 8, preferablyto the integer 8 as shown in FIG. 5, the integer 6 being, with an advantage, spaced apart from the integers 12 in the equilibrium state'and in normal running. In this case the integers 12 provide extra suspension stiffness only above a compression threshold of the suspension and act as a kind of a resilient abutment or stop.

FIG. 5 shows how the machine operates when experiencing a rolling torque produced by a lateral force F. Shown diagrammatically near the throat of each pump 16 is a valve 17 which can provide a variable closure of the supply line for'the corresponding integer 12. This feature is a means of increasing the stiffness of the integer 12 in response to rapid excitations without any greatly altered response to slow excitations.

Of course, the extra stiffness introduced by the integers 12 into pneumatic cushion suspensions is of use not only for the normal case of cushions at a positive pressure for the environment but also in the opposite case of ground effect machines having cushions at a negative pressure to the environment, as described inter alia in US. Pat. No. 3,580,181. FIG. 6 illustrates a use of this kind; like elements have the same reference number, plus an apostrophe sign, as in the previous embodiment.

The structure 1 of the machine shown in FIG. 6 is guided by appopriate means 19, such as runners or pressure-fluid cushions, along an overhead track 2' below which a bearing cushion 3 at a negative pressure P'l extends. By way of apertures in a plate or disc or the like 6 having skirts 5, cushion 3 communicates with an enclosure 10 serving as a suspension chamber which is at a negative pressure P2 more intense than the negative pressure Pl -i.e., in absolute terms the pressure P2 is lower than the pressure P'l. The pressure P2 is produced by an exhauster 20 communicating via an orifice 4 with the enclosure 10'; the same is closed by a flexible hermetic wall 9' and comprises tubular air chambers 12' which are secured to the integers 6 and 8 by plates 13'. The integers 12 are therefore interposed in chamber 10 between the integers 6 and 1 so that the reaction arising from any compression of the' integers 12 tends to move the skirts 5' towards the track 2. I

As in the previous embodiments in the operative state i.e., when not in the normal state the pressure P3 of the, fluid in the integers 12' is higher than the pressure P2 in the suspension chamber 10'. For this purpose the integers 12 can be, e.g., connected to the outside environment via vent ducts 18 andthus make use of the static pressure of the environment, in which event no special pump, such as the static pumps 16 of FIGS. 4 and 5, is needed for the integers 12.

Another way of producing the required relative overpressure inthe integers 12 without any special booster is to use a main pressure intake 21 which is shown in FIG. 7 and which is disposed opposite the outputof a.

fan 22 delivering to a header 23 from which the pressure fluid forthe cushions is sampled through supply ducts 4 by means disclosed in US. Pat. Application Ser. No. 75,474 of Sept. 25, 1970. The integer 21 is disposed upstream of the ducts 4. A loss of head occurs therein but does not affect the integer 21, and so the pressure P3 in the integers 12 is higher than the pressure P2 in the chambers 10.

Referring to FIG. 8, a ground effect machine 1 is guided on an inverted-T track '2 by way of pressure fluid cushions; some, 38, of the cushions act as lift cushions and bear on horizontal surfaces 28 of the track while others, 3G, of the cushions act as guide cushions and bear on opposite vertical surfaces 26 of track 2. In this example, which refers to quadrilateral cushions having four containing means of the kind disclosed by French Pat. No. 1,602,658 of June 28, 1968, tubular air chambers 128 are associated with the lift cushions 3S and tubular air chambers 12G are associated with the guide cushions 3G.

The chambers 12G are supplied directly by dynamic pressure intakes 24 which extend to the outside of the machine 1 and face towards the front thereof, whereas the chambers 128, which are connected to form pairs by way of flexible connecting hoses 15, are supplied by static pumps 16; in the example shown the inducing flow of the static pumps is provided by a gas turbine engine M by way of a distributor 25 whence supply ducts C extend over the whole length of the vehicle to feed all the cushions, the nozzles 14 of the pumps 16 being connected to the ducts C.

Distributor 25 is controlled by a manometric detector 26 having a diaphragm responsive to the difference between the pressures of opposite guide cushions 36, such pressures acting on the detector 26 through ducts 27, 27 extending to sensing elements in the guide cushions. Distributor 25 is disposed in a bleed pipe 28 connected to the compressor of engine M and outputs to lines 29 having check valves 30 and connected to the ducts C. Clearly, therefore, the inducing flow supplied to injectors M of static pumps 16 via ducts C is controlled by distributor 25 in dependence upon the pressure difference between opposite guide cushions 3G by means of detector 26. Distributor 25 is so devised that the delivered inducing flow is proportional to the detected pressure difference, whatever the sign thereof. Means which are not shown may or may not be provided to amplify the dynamic pressure intaken at the intakes 2d. 7

As a variant or additionally, a distributor 25 in FIG. 9, which is similar to the distributor 25, is adapted to inflate all the tubular air chambers in dependence upon a pressure difference detector 26' which is similar to the detector 26 but which is associated with sidewind pressure intakes 31 disposed on the structure side walls and facing laterally in opposite directions, the corresponding pressures being transmitted through ducts 27 on either sideof the diaphragm of detector 26'.

The following results can be achieved by the features hereinbefore described for controlling tubular air chamber pressure in dependence upon various parame ters: 1

In the event of gusts of wind, turns and general disturbances affecting the trim of the machine, the suspension of all the lift cushions 35 is stiffened as a result of inflation of the tubular air chambers 128. Similar considerations apply to the suspension provided by the guide cushions 36, which is stiffened in the eventof wind gusts and other disturbances including largeradius turns. For a narrow-radius turn, however, the vehicle must slow down, in which event the stiffness of the guide cushion suspensions decreases, thusmaking it easier for the vehicle to take the curve.

Since the guide cushion chambers 120 are supplied from dynamic pressure intakes 24 visible in FIG. 8, the pressure in the integers 12G depends upon the speed of the machine. If the detector 26 detects any pressure difference between opposite guide cushions, pressure fluid goes through distributer 25 to all the tubularair chmabers MS of the lift cushions 3S, whatever the sign of the detected pressure difference. Suchpressure difference is therefore used to control tubular air chamber pressure in dependence upon cross winds, centrifugal force and tilting of the machine. Also, since the cross wind pressure operative near the intakes 31 of FIG. 9 has a direct effect, all cushions stiffen in the event of wind gusts.

The embodiments described relate to ground effect machines having cushions contained by lateral physical skirts, but the. invention is of course also of use for cushions contained by other means, more particularly cushions contained by fluid curtains.

We claim:

l. A pneumatic suspension system for a groundeffect machine cushion confined bycushion-seal means carried by a movable plate responsive to a cushion pressure P1 acting on one side thereof and to an oppos ing pressure P2 acting on the other side thereof and obtaining in a deformable suspension plenum which is enclosed between said movable plate and an opposite structure plate and which is laterally bounded by a flexible fluidtight wall extending between said plates, wherein the improvement comprisesa pneumatic tube housed in said plenum in inwardly spaced relationship with respects to said flexible fluidtight wall and adapted to be inflated to a pressure P3 above said opposing pressure P2 and to bear against said movable plate, whereby extra stiffness is provided in the suspension.

2. A system according to claim 1, wherein one of said plates is, under normal or rest condition of said suspension plenum, spaced from said pneumatic tube, and only engages the same after an amount of displacement of said movable plate towards said structure plate, whereby said extra stiffness is provided in the suspension contingent to a minimum threshold deformation of said plenum.

3. A system according to claim 1, wherein the inflation pressure of the pneumatic tube is under the control of a parameter controlling the trim of the machine.

4. A system according to claim .3 wherein the pneumatic tube is inflated by pressure fluid tapped directly from the cushion fluid supply, in parallel with but with less pressure drop than pressure fluid intake means for the suspension plenum. i

5. A system according to claim 4 wherein the pneumatic tube is inflated from a total pressure tap on the discharge of a fan delivering pressure fluid forthecushion. i

6. A system according to claim 1 wherein the pneumatic tube is supplied by means of an ejector sucking from the deformable suspension 'plenum.

7. A system according to claim 6 wherein the pneu matic tube is inflated by means of a variable flow ejector comprising a flow controlvalve.

8. A system according to claimll wherein the machine is adapted to move along a track with the interposition of lift cushions producing a lifting force having a vertical component and guide cushions which are disposed opposite one another and which produce forces having balanced horizontal components, the inflation of a pneumatic tube relative to the suspension of a cushion being controlled by a detectorsensing the pressure difference between two opposite guide cushions, the inflation pressure depending upon the absolute pressure difference thus sensed.

9. A system according to claim 8 wherein the detector is associated with all the pneumatic tubes for lift cushion suspension.

10. A system according to claim 1, wherein the inflation pressure of the pneumatic tube is under the control of pressure taps disposed at outside places of the 12. A system according to claim 1 wherein the pneumatic tube which extend between the fixing flanges bematic tube is secured along a contact surface by means ing, when the movable plate in equilibrium position, of two fixing flanges disposed opposite one another, the arcs of the same circle. two opposite segments of the flexible wall of the pneu- 

1. A pneumatic suspension system for a ground-effect machine cushion confined by cushion-seal means carried by a movable plate responsive to a cushion pressure P1 acting on one side thereof and to an opposing pressure P2 acting on the other side thereof and obtaining in a deformable suspension plenum which is enclosed between said movable plate and an opposite structure plate and which is laterally bounded by a flexible fluidtight wall extending between said plates, wherein the improvement comprises a pneumatic tube housed in said plenum in inwardly spaced relationship with respects to said flexible fluidtight wall and adapted to be inflated to a pressure P3 above said opposing pressure P2 and to bear against said movable plate, whereby extra stiffness is provided in the suspension.
 2. A system according to claim 1, wherein one of said plates is, under normal or rest condition of said suspension plenum, spaced from said pneumatic tube, and only engages the same after an amount of displacement of said movable plate towards said structure plate, whereby said extrA stiffness is provided in the suspension contingent to a minimum threshold deformation of said plenum.
 3. A system according to claim 1, wherein the inflation pressure of the pneumatic tube is under the control of a parameter controlling the trim of the machine.
 4. A system according to claim 3 wherein the pneumatic tube is inflated by pressure fluid tapped directly from the cushion fluid supply, in parallel with but with less pressure drop than pressure fluid intake means for the suspension plenum.
 5. A system according to claim 4 wherein the pneumatic tube is inflated from a total pressure tap on the discharge of a fan delivering pressure fluid for the cushion.
 6. A system according to claim 1 wherein the pneumatic tube is supplied by means of an ejector sucking from the deformable suspension plenum.
 7. A system according to claim 6 wherein the pneumatic tube is inflated by means of a variable flow ejector comprising a flow control valve.
 8. A system according to claim 1 wherein the machine is adapted to move along a track with the interposition of lift cushions producing a lifting force having a vertical component and guide cushions which are disposed opposite one another and which produce forces having balanced horizontal components, the inflation of a pneumatic tube relative to the suspension of a cushion being controlled by a detector sensing the pressure difference between two opposite guide cushions, the inflation pressure depending upon the absolute pressure difference thus sensed.
 9. A system according to claim 8 wherein the detector is associated with all the pneumatic tubes for lift cushion suspension.
 10. A system according to claim 1, wherein the inflation pressure of the pneumatic tube is under the control of pressure taps disposed at outside places of the ground effect machine, the pressure taps being dynamic pressure scoops facing towards the front of the machine or sidewind intakes opening on to the machine sides.
 11. A system according to claim 1 wherein the cushion contains fluid at a negative pressure relatively to the environment, the pneumatic tube in the suspension being connected to a static pressure tap in the ambient medium.
 12. A system according to claim 1 wherein the pneumatic tube is secured along a contact surface by means of two fixing flanges disposed opposite one another, the two opposite segments of the flexible wall of the pneumatic tube which extend between the fixing flanges being, when the movable plate in equilibrium position, arcs of the same circle. 